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Therefore, the CPC's own OS (in combination with AmsDOS), and [[CP/M|CP/M]] (plus) and FutureOS (since 1989) were the only two known OSes for the series, but the question remained: since most CPCs have 128K (most C64 only have 64K), a screen-resolution of 320x200 with 4 colours (C64 only has 2 colours for each 8x8 area in 320x200) and some more advantages, why not have something similar? So the SymbOS-Project was born. SymbOS stands for "SYmbiosis Multitasking Based Operating System". SymbOS is a demonstration of what has been achieved on the CPC: real preemptive multitasking, dynamic memory-management for up to 1024K and a totaly MS-Windows-like GUI are the three most important features.

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Even the Z80 8-bit CPU is able to run a pre-emptive multitasking environment. Missing mechanisms like memory protection, which are often called as a condition for multitasking, are system stability issues only. The MP/M operating system already proved, that multitasking on Z80 computers is possible, but it was not executable on home computers. Today different implementaions of multitasking OS exists for Z80 based systems e.g. Roseanne for the PcW or Doors for the Spectrum.

While the MOS Technology 6502 can not move the stack, the Z80 can freely replace it to any position in the memory, which is more or less a condition for pre-emptive multitasking. The existance of an alternative register set accelerates the content switching between the tasks dramatically. The restriction of Z80 systems to a 64 kB address space can be solved with bank switching. In this way computers like the Amstrad CPC and PCW, MSX, Enterprise or SAM Coupé are able to access hundred or thousand of kilobytes of memory.

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